feat: Station Control amp parity + all amps, Help→Send log to F4BPO, bulk-edit frequency, fix Cluster midnight sort

- Station Control: the amplifier panel is now the exact same card as the FlexRadio panel (extracted shared AmpCard: OPERATE/STANDBY, ON/OFF, power level, output-power bar, live FWD/ID/temp meters). Every configured amp gets its own card — no dropdown.
- Help → "Send log to F4BPO" (only when SMTP is configured): e-mails opslog.log + previous session + crash log to the developer. New email.SendFiles for multi-attachment.
- Bulk edit: new "Frequency (MHz)" field sets freq_hz AND recomputes band; out-of-band values rejected. Fixes a run logged on a stale/default freq after CAT dropped.
- Cluster: Time column sorted lexically on the HHMMZ string, so spots after 0000Z sorted below 2359Z and looked frozen at the UTC rollover. Now sorts by real arrival time.
- Also folds in the DVK auto-CQ/2-column layout and Station Control dashboard batch (changelog 0.20.10, EN+FR).

internal/email/email.go

@@ -41,6 +41,16 @@ func (c Config) opts() []mail.Option {
 
 // Send delivers a plain-text email to `to`, optionally attaching a file.
 func Send(cfg Config, to, subject, body, attachPath string) error {
+	var attach []string
+	if attachPath != "" {
+		attach = []string{attachPath}
+	}
+	return SendFiles(cfg, to, subject, body, attach)
+}
+
+// SendFiles is like Send but attaches any number of files (missing paths are
+// skipped by the mail library at send time).
+func SendFiles(cfg Config, to, subject, body string, attachPaths []string) error {
 	if cfg.Host == "" {
 		return fmt.Errorf("SMTP server not configured")
 	}
@@ -65,8 +75,10 @@ func Send(cfg Config, to, subject, body, attachPath string) error {
 	}
 	m.Subject(subject)
 	m.SetBodyString(mail.TypeTextPlain, body)
-	if attachPath != "" {
-		m.AttachFile(attachPath)
+	for _, p := range attachPaths {
+		if p != "" {
+			m.AttachFile(p)
+		}
 	}
 	client, err := mail.NewClient(cfg.Host, cfg.opts()...)
 	if err != nil {

internal/qso/qso.go

@@ -792,6 +792,31 @@ func (r *Repo) BulkSetField(ctx context.Context, ids []int64, column, value stri
 	return n, nil
 }
 
+// BulkSetFrequency sets freq_hz AND band together on every listed QSO. Kept
+// separate from BulkSetField because frequency is numeric and must keep the band
+// consistent — the main use is fixing a batch that was logged on a stale/default
+// frequency after CAT dropped. freqHz "" is not allowed (caller validates).
+func (r *Repo) BulkSetFrequency(ctx context.Context, ids []int64, freqHz int64, band string) (int64, error) {
+	if len(ids) == 0 {
+		return 0, nil
+	}
+	ph := make([]string, len(ids))
+	args := make([]any, 0, len(ids)+3)
+	args = append(args, freqHz, band, db.NowISO())
+	for i, id := range ids {
+		ph[i] = "?"
+		args = append(args, id)
+	}
+	res, err := r.db.ExecContext(ctx,
+		`UPDATE qso SET freq_hz = ?, band = ?, updated_at = ? WHERE id IN (`+strings.Join(ph, ",")+`)`,
+		args...)
+	if err != nil {
+		return 0, fmt.Errorf("bulk set frequency: %w", err)
+	}
+	n, _ := res.RowsAffected()
+	return n, nil
+}
+
 // SetExtra merges ONE key into a QSO's extras JSON without rewriting the rest of
 // the row. A slow caller that only wants to stamp its own app field (e-mailing a
 // QSL card, saving a recording) must not do a full-row Update: the row it read may